Subject: Re: [mobile-ip] Mobile IPv6 - Issue 72 (Forwarding from previous CoA)

From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 16 Sep 2002 09:23:47 -0700

Hello Jim,

At this point, since we are trying to finish up comments
received during Last Call, I'd rather try to avoid making
major document reorganizations.  I don't think the forwarding
mechanism described in the base specification belongs in
the Fast Handover document, because it doesn't define any
new messages or protocol.

Regards,
Charlie P.

---

From: [email-masked]
Date: Mon, 16 Sep 2002 09:11:01 -0700

James

Currently as the base specification describes the functionality it is implemented with Home Agent functionality. There is nothing in addition to the "normal" Home Agent behavior. This feature doesn't set any additional requirements on access router nor home agent. If an access router has home agent support enabled and the SA in place you have the feature. There is nothing to be defined. The SA is the very same SA as with the Home Agent, provided that it can be shared among a number of home agents.  We don't need to describe hoe this SA is set in place, as we don't define how we set the SA for the home agent, do we.

If the feature is to be moved to some other document, please not that there is in the base specification some references to it for MN. Particularly the behavior of the Home Agent list needs to be also changed if the section "11.6.6.Forwarding from a Previous care-Of Address" is moved out of the doc. Otherwise the base line is referring to something that doesn't exists. If the home agent list processing description is changed, the conformance is affected and the MN implementations need to be updated. 

Regards Hannu

-----Original Message-----
From: ext James Kempf [mailto:[email-masked]]
Sent: 16 September, 2002 8:20 AM
To: Flinck Hannu (NRC/MTView); Patil Basavaraj (NET/Dallas);
[email-masked]
Subject: Re: [mobile-ip] Mobile IPv6 - Issue 72 (Forwarding from
previous CoA)

Hannu,

> Since this feature is implemented as part of normal HA behavior and it has
been there for ages, I would like to suggest to place it to the annex of the
document rather than cut it out.

The proposal isn't to drop it the feature, but to move it to a separate
document. The fast handover document already contains the basic functionallity,
so it is more logical to put it into that document.

> In some scenarios this would still be a useful deployment of Home Agents,
especially if they have a group SA among themselves. This is a special case of
course, and it is not able to provide the same seamless operation as Fast
Handovers would.

I'm not sure I understand your comment. This functionality has nothing to do
with the Home Agent, it has to do with the Access Router. Sometimes an Access
Router that provides this functionality is called an "on-link" Home Agent, is
that what you are talking about? If so, I don't understand your comment about an
SA. An SA among a group of such "on-link" Home Agents isn't equivalent to an SA
between the "on-link" Home Agents and the Mobile Node. Should such an SA exist,
the Mobile Node would have to verify it, and the pre-existence of such an SA
between an Access Router and a random Mobile Node is highly unlikely in the
first place. So the security aspects of providing this functionality are
currently undefined. Rather than delay the base spec any longer to define them,
why not consolidate the functionality to another spec which is trying to provide
that functionality, and deal with the security aspects at our leisure there?

            jak

> Regards Hannu
>
> -----Original Message-----
> From: ext [email-masked] [mailto:[email-masked]]
> Sent: 13 September, 2002 2:34 PM
> To: [email-masked]
> Subject: [mobile-ip] Mobile IPv6 - Issue 72 (Forwarding from previous
> CoA)
>
>
> Issue 72: Forwarding from Previous Care of Address
> --------------------------------------------------
>
> http://www.piuha.net/~jarkko/publications/mipv6/issues/issue72.txt
>
> Section 11.6.6 of the Mobile IPv6 specification describes the ability
> to forward packets from a previous CoA to the new CoA as a result of
> the MN connecting to a new link.
>
> Since the BU sent to an HA on the previous link requires the same
> security as the BUs sent to the MNs Home Agent (on home link), this is
> quite a difficult proposition from an implementation and deployment
> perspective. So,
>
> Recommendation:
> ---------------
>
> The Mobile IP WG is currently working on fast handoffs for Mobile IPv6
> which deals with the aspect of forwarding packets from the previous
> CoA to the new CoA (draft-ietf-mobileip-fast-mipv6-04.txt).
>
> Hence this entire feature can effectively be dropped out of the base
> Mobile IPv6 specification and pursued independently as a separate
> feature for IPv6 mobility.
> All text associated with the forwarding from previous CoA will be
> deleted from the current specification.
>
> If you have any concerns or views on why this feature should be a part
> of the base specification, please post them to the list.
>
> -Basavaraj
>
>
>
>
>

---

From: "James Kempf" <[email-masked]>
Date: Mon, 16 Sep 2002 09:55:25 -0700

Hannu

>
> Currently as the base specification describes the functionality it is
implemented with Home Agent functionality. There is nothing in addition to the
"normal" Home Agent behavior. This feature doesn't set any additional
requirements on access router nor home agent. If an access router has home agent
support enabled and the SA in place you have the feature. There is nothing to be
defined. The SA is the very same SA as with the Home Agent, provided that it can
be shared among a number of home agents.  We don't need to describe hoe this SA
is set in place, as we don't define how we set the SA for the home agent, do we.

The document refers to this functionality in the context of access routers, not
home agents. For example,
see Section 7.2:

  -  To allow a mobile node to send a Binding Update to a router on
       the link on which its previous care-of address is located, for
       purposes of establishing forwarding from this previous care-of
       address to its new care-of address (Section 11.6.6).

There are other such references throughout the document.

This confusion (is it an access router functionality or a home agent
functionality?) is part of the reason why I think it should be moved into the
fast handover document.

From my reading of the rest of the spec, with the exception of FoPCoA, there are
no requirements put on the access router whatsoever, so a standard IPv6 router
could be used. I believe this was one of the original design goals of MIPv6, for
example, see Section 2:

    -  There is no longer any need to deploy special routers as
       "foreign agents" as are used in Mobile IPv4.  In Mobile IPv6,
       mobile nodes make use of IPv6 features, to operate in any
       location without any special support required from the local
       router.

This feature compromises this basic design goal, and I believe it should be
moved to the fast handover spec, which explicitly requires changes in the access
router. Another possibility is that this design goal could be removed from the
MIPv6 spec, but I think that would be a mistake, since the rest of the spec
conforms with the design goal. Or the MIP group could make a recommendation that
all IPv6 routers be required to implement this functionality, and take the issue
to the IPv6 Working Group. Of these three, I think the easiest is to move it
into a spec that discusses MIPv6 handover directly and talks about specialized
MIPv6 access router functionality.

            jak